Heretofore, it has been recognized that in the measurement of fluid flow, laminar flow conditions are preferred to achieve more accurate flow measurement. It has also long been recognized that a continuing problem in measurement of fluid flow is establishing a linear relationship between the measured flow and a signal varying with the flow. Various techniques have been employed to create laminar flow in a turbulent flow condition and to linearize the relationship between a signal varying with measured flow and the rate of flow passing a transducer. The various techniques heretofore used in the measurement of the rate of flow of a fluid have been acceptable so long as the flow conditions are reasonably well defined.
Where the conditions of the fluid flow to be measured are not well defined, there has developed a need for a transmitter and a flow indicator that has an acceptable accuracy factor. An example of a fluid system wherein the flow cannot be well defined and includes pulsating flow conditions are vehicle mounted systems. For example, a fluid system mounted on a truck chasis by necessity results in only a few very short straight runs of pipe that have been defined as the most desirable location for a fluid flow transducer. Thus, fluid systems on a vehicle chasis usually require the measurement of flow in a turbulent flow condition. Furthermore, the fluid discharge of such vehicle mounted systems is also pulsating which compounds the problem of producing an accurate flow measurement.
When measuring flow in a large fixed installation, with a reasonably long productive life, the cost of the fluid measuring transducer and indicator is usually not considered to be a significant part of the total system cost. However, when measuring fluid flow in a vehicle mounted system, which may have only a relatively short productive life span, the cost of the fluid flow measuring transducer and indicator becomes a more significant factor. Thus, while some of the previously used techniques for measurement of flow are available for the vehicle mounted system, the cost of such techniques are prohibitive and out of proportion to the overall cost of the system. Any fluid flow measuring system for a vehicle mounted flow system requires a careful analysis of the costs involved.